Qatl-e-aam is an Urdu phrase which means killing of common men (or persons really, not men as such). So any killing which is just for the purpose of killing anyone who is present at the moment and not directed at someone specific, is qatl-e-aam. However the phrase is used for praising beauty, the way one could call someone’s beauty a killer.

As for this song here, it’s a ghazal with a relatively long meter, even though it might not sound like a typical ghazal.

this is the market of the heart, and it’s time for the first sale,
(and that’s why) I am offering you this thing worth millions for peanuts.

[sarraafa is the word used for the market of gold and silver jewellery.
‘bohni’ is the first sale of the day and it is believed that it’s bad for business to let a customer go back without buying until you have made the first sale. Hence in businesses where bargaining is common, shopkeepers often offer low rates, though at times it’s used as an excuse as well.]